In the module docstring, clarify that this is used to register pickle support for extension types, not classes.
In the module docstring, clarify that this is used to register pickle
support for extension types, not classes.

pickle():  If the type is a class or if the reduction function is not
           callable, raise a TypeError.

constructor():  If the constructor is not callable, raise TypeError.

This (partially) closes SourceForge patch #101859.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator